The present invention relates to a device for controlling engine RPM through a feedback loop so as to equalize the same to a target or reference engine RPM established according to engine conditions.
With conventional engine RPM control devices, any change in the engine RPM due to an engine load torque variation, such as when the load status is shifted from the ON to the OFF condition or vice versa, is minimized under predictive control on direct detection of such a load status change. However, the actuator for controlling the throttle valve is subjected to a delay time in operation, and it takes a certain interval of time for the engine RPM to vary in response to any desired opening of the throttle valve. Therefore, any change in the engine RPM caused at the time of a variation in the load condition cannot be eliminated solely by predictive control. The prior control device is particularly disadvantageous in that the engine tends to be forcibly stopped when the engine load is shifted from the OFF status to the ON status with a large and abrupt torque variation.